Chemistry is the science that explores matter, its properties, and... Show more
Chemistry419 views·Updated May 25, 2026·3 pagesComprehensive Chemistry Regents Review Guide
1 / 3
1
of 3
Classification of Matter & Atomic Structure
Ever wonder what everything around you is actually made of? All matter falls into either pure substances (elements and compounds) or mixtures (homogeneous or heterogeneous). We separate mixtures using different methods based on their properties: distillation for different boiling points, chromatography for varying molecular polarity, and filtration for different particle sizes.
Atoms are the building blocks of everything! To understand them, remember that atomic mass - atomic number = number of neutrons. When electrons move between energy levels in atoms, they release energy as light, creating distinctive bright line spectra that act like atomic fingerprints.
The periodic table organizes elements logically, with metals on the left (good conductors, malleable, low electronegativity) and nonmetals on the right (poor conductors, brittle, high electronegativity). As you move across a period, electronegativity and ionization energy increase, while moving down a group decreases both.
Quick Tip: Remember that some elements exist in different forms called allotropes - like carbon appearing as both diamonds and graphite - same element, completely different properties!
Understanding bonds between atoms is crucial. Covalent bonds share electrons between nonmetals, creating compounds with low melting points that don't conduct electricity. Ionic bonds transfer electrons (like in Ca(NO₃)₂), forming strong compounds with high melting points that conduct electricity when dissolved or melted.
2
of 3
Chemical Language & Reactions
Chemical formulas are like recipes that tell you exactly what's in a compound. Molecular formulas show the actual number of atoms (like H₂O), while empirical formulas give the simplest whole-number ratio (like CH₂O for glucose, C₆H₁₂O₆).
Chemical reactions come in five main types that you'll need to recognize: synthesis (combines elements), decomposition (breaks compounds down), single replacement (one element replaces another), double replacement (elements swap partners), and combustion (always produces CO₂, H₂O, and heat).
The mole concept connects the microscopic world of atoms with measurable quantities in the lab. To convert between grams and moles, use the formula: moles = mass ÷ molar mass. When balancing equations, remember that atoms must be conserved - what goes in must come out!
Remember: Phase changes involve energy changes! When a substance melts or boils, it absorbs energy (endothermic), and when it condenses or freezes, it releases energy (exothermic).
Gas laws help predict how gases behave under different conditions. The key relationships are Boyle's Law , Charles' Law , and the Ideal Gas Law . Vapor pressure increases with temperature and surface area but decreases with stronger intermolecular forces.
3
of 3
Acids, Bases & Nuclear Chemistry
Acids and bases are everywhere - from the vinegar in your kitchen to the soap in your bathroom! Acids have pH values below 7, taste sour, and produce hydrogen gas with certain metals. Bases have pH values above 7 and feel slippery. The pH scale runs from 0-14, with each number representing a tenfold change in hydrogen ion concentration.
Two important acid-base theories to know: Arrhenius theory says acids produce H⁺ ions in water while bases produce OH⁻ ions. Bronsted-Lowry theory describes acids as proton donors and bases as proton acceptors, forming conjugate pairs during reactions.
Electrochemistry explores how chemical reactions can produce electricity (voltaic cells) or how electricity can drive chemical reactions (electrolytic cells). In these cells, oxidation (loss of electrons) happens at the anode, while reduction (gain of electrons) occurs at the cathode.
Nuclear Fact: Unlike chemical reactions that involve electron rearrangements, nuclear reactions change the atom's nucleus itself through processes like radioactive decay, fission (splitting atoms), or fusion (combining atoms).
Organic chemistry deals with carbon-based compounds found in living things. Different functional groups give organic molecules their properties. Remember that saturated hydrocarbons (alkanes) have only single bonds, while unsaturated hydrocarbons have double or triple bonds, making them more reactive. Generally, the larger the organic molecule, the stronger its intermolecular forces and the higher its melting and boiling points.
We thought you’d never ask...
What is the Knowunity AI companion?
Our AI companion is specifically built for the needs of students. Based on the millions of content pieces we have on the platform we can provide truly meaningful and relevant answers to students. But its not only about answers, the companion is even more about guiding students through their daily learning challenges, with personalised study plans, quizzes or content pieces in the chat and 100% personalisation based on the students skills and developments.
Where can I download the Knowunity app?
You can download the app in the Google Play Store and in the Apple App Store.
Is Knowunity really free of charge?
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
Similar Content
Most popular content: Acid-base Chemistry
2Most popular content in Chemistry
9Most popular content
9Can't find what you're looking for? Explore other subjects.
Students love us — and so will you.
4.6/5App Store
4.7/5Google Play
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan SiOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha KlichAndroid user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
AnnaiOS user
Chemistry419 views·Updated May 25, 2026·3 pagesComprehensive Chemistry Regents Review Guide
Chemistry is the science that explores matter, its properties, and how substances interact. This summary covers essential high school chemistry concepts from atomic structure to organic chemistry, breaking down complex ideas into manageable chunks you'll need for exams and labs.
1
of 3Sign up to see the content. It's free!
- Access to all documents
- Improve your grades
- Join milions of students
Classification of Matter & Atomic Structure
Ever wonder what everything around you is actually made of? All matter falls into either pure substances (elements and compounds) or mixtures (homogeneous or heterogeneous). We separate mixtures using different methods based on their properties: distillation for different boiling points, chromatography for varying molecular polarity, and filtration for different particle sizes.
Atoms are the building blocks of everything! To understand them, remember that atomic mass - atomic number = number of neutrons. When electrons move between energy levels in atoms, they release energy as light, creating distinctive bright line spectra that act like atomic fingerprints.
The periodic table organizes elements logically, with metals on the left (good conductors, malleable, low electronegativity) and nonmetals on the right (poor conductors, brittle, high electronegativity). As you move across a period, electronegativity and ionization energy increase, while moving down a group decreases both.
Quick Tip: Remember that some elements exist in different forms called allotropes - like carbon appearing as both diamonds and graphite - same element, completely different properties!
Understanding bonds between atoms is crucial. Covalent bonds share electrons between nonmetals, creating compounds with low melting points that don't conduct electricity. Ionic bonds transfer electrons (like in Ca(NO₃)₂), forming strong compounds with high melting points that conduct electricity when dissolved or melted.
2
of 3Sign up to see the content. It's free!
- Access to all documents
- Improve your grades
- Join milions of students
Chemical Language & Reactions
Chemical formulas are like recipes that tell you exactly what's in a compound. Molecular formulas show the actual number of atoms (like H₂O), while empirical formulas give the simplest whole-number ratio (like CH₂O for glucose, C₆H₁₂O₆).
Chemical reactions come in five main types that you'll need to recognize: synthesis (combines elements), decomposition (breaks compounds down), single replacement (one element replaces another), double replacement (elements swap partners), and combustion (always produces CO₂, H₂O, and heat).
The mole concept connects the microscopic world of atoms with measurable quantities in the lab. To convert between grams and moles, use the formula: moles = mass ÷ molar mass. When balancing equations, remember that atoms must be conserved - what goes in must come out!
Remember: Phase changes involve energy changes! When a substance melts or boils, it absorbs energy (endothermic), and when it condenses or freezes, it releases energy (exothermic).
Gas laws help predict how gases behave under different conditions. The key relationships are Boyle's Law , Charles' Law , and the Ideal Gas Law . Vapor pressure increases with temperature and surface area but decreases with stronger intermolecular forces.
3
of 3Sign up to see the content. It's free!
- Access to all documents
- Improve your grades
- Join milions of students
Acids, Bases & Nuclear Chemistry
Acids and bases are everywhere - from the vinegar in your kitchen to the soap in your bathroom! Acids have pH values below 7, taste sour, and produce hydrogen gas with certain metals. Bases have pH values above 7 and feel slippery. The pH scale runs from 0-14, with each number representing a tenfold change in hydrogen ion concentration.
Two important acid-base theories to know: Arrhenius theory says acids produce H⁺ ions in water while bases produce OH⁻ ions. Bronsted-Lowry theory describes acids as proton donors and bases as proton acceptors, forming conjugate pairs during reactions.
Electrochemistry explores how chemical reactions can produce electricity (voltaic cells) or how electricity can drive chemical reactions (electrolytic cells). In these cells, oxidation (loss of electrons) happens at the anode, while reduction (gain of electrons) occurs at the cathode.
Nuclear Fact: Unlike chemical reactions that involve electron rearrangements, nuclear reactions change the atom's nucleus itself through processes like radioactive decay, fission (splitting atoms), or fusion (combining atoms).
Organic chemistry deals with carbon-based compounds found in living things. Different functional groups give organic molecules their properties. Remember that saturated hydrocarbons (alkanes) have only single bonds, while unsaturated hydrocarbons have double or triple bonds, making them more reactive. Generally, the larger the organic molecule, the stronger its intermolecular forces and the higher its melting and boiling points.
We thought you’d never ask...
What is the Knowunity AI companion?
Our AI companion is specifically built for the needs of students. Based on the millions of content pieces we have on the platform we can provide truly meaningful and relevant answers to students. But its not only about answers, the companion is even more about guiding students through their daily learning challenges, with personalised study plans, quizzes or content pieces in the chat and 100% personalisation based on the students skills and developments.
Where can I download the Knowunity app?
You can download the app in the Google Play Store and in the Apple App Store.
Is Knowunity really free of charge?
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
Similar Content
Most popular content: Acid-base Chemistry
2Most popular content in Chemistry
9Most popular content
9Can't find what you're looking for? Explore other subjects.
Students love us — and so will you.
4.6/5App Store
4.7/5Google Play
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan SiOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha KlichAndroid user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
AnnaiOS user